Mesa 20/20 Deep Mod

[francm]

A lot of people want to do this mod on their 20/20 but info can be hard to find.

Basically, the deep mod consists in removing the high pass filtering on the input stage on the 20/20 amplifier. Its is very simple. All you need to do is remove the C1/C3 capacitors on the tube board. The image below shows an original 20/20 tube board. To perform the mod, you need to remove two yellow capacitors with the tapered end on the "+" marking of the PCB.

The Ch B capacitor is the first device on the lower left hand side.
The Ch A capacitor is the 3rd device after the ch b tube socket (the first tube socket from the left) on the lower part of the board. Right under the ChA marking, between the two 12AX7 sockets.

I hope this is clear enough.

 

[sir riff a lot]

has anyone here done the mod ?

did you like the results?

I'm curious about doing mine, but I already like the 20/20 and dont want to mess with it.

but then again, if it gives a bit more "thump" , I would be keen

 

[crane]

Mine is still under warranty, but I'll do the mod in a few month. I will simply use a switch to bypass the capacitors, so the mod could be reversed with a simple "clic"

 

[INDI]

What is the result of this modification? How it will affect the sound?

 

[francm]

What is the result of this modification? How it will affect the sound?

Ummm.... did you read the first post?

Gives you more bass AND makes the amp appear to sound less nasally because of the better frequency response

 

[Monsta-Tone]

Do you have any clips?

How much more bass does it have after the mod?
I've been looking at a 2:90, and while I realize that the 20/20 will never have the thump that 8 6L6's will, can it come even close?

 

[MusicManJP6]

This may be a stupid question, but does this mod apply to a DC-3 as well?

 

[francm]

Do you have any clips?
How much more bass does it have after the mod?
I've been looking at a 2:90, and while I realize that the 20/20 will never have the thump that 8 6L6's will, can it come even close?

No clips.

The modded 20/20 does have some thump BUT it compresses at band volumes. The extra bass is definitely noticeable and to me, it made a big difference. With the mod, its a great small amp that can definitely get loud. It has a great vocal quality to its sound. Great combination with a Strat, esp. if you play blues/rock and some 70's classic rock. It would make a neat little jazz amp too.

Does it come close to the 2:90? No. I replaced the 20/20 with a 2:90. I prefer the 2:90's more transparent sound, extra high end and overall balls. Its just way too loud for most situations. I always run it in 1/2 power mode. The 2:90, when run louder, provides more definition and less compression. Great for fast, articulate rhythms.

 

[tofisi]

Because my plate is not the same like a picture above. For moding my mesa 20/20 shoud I remove this two yallow capacitor? thanks for replay

PICTURE

 

[francm]

Because my plate is not the same like a picture above. For moding my mesa 20/20 shoud I remove this two yallow capacitor? thanks for replay

Yup, those would be them.

 

[tofisi]

Because my plate is not the same like a picture above. For moding my mesa 20/20 shoud I remove this two yallow capacitor? thanks for replay

Yup, those would be them.

Thanks

 

[Dewdman42]

I am thinking about doing the deep mod, or possibly making it switchable. here's the question though, if the deep mod simply removes a high pass filter being executed by the electronic component, would it not be possible to deep mod the 20/20 and then when you want to have your sound be more stock, just apply an EQ to the end of the preamp chain just before sending to the 20/20 in order to accomplish essentially the same thing?

My guess is that for lead sounds I'm gonna prefer without the mod and for chunky rythmns I'm gonna prefer the mod.

 

[crane]

It is a filter, so it cuts frequencies. Applying an eq won't help.
But you can make the deep mod using switches, as I plan to do, so you can apply or remove it as you want.

 

[Dewdman42]

Uhmm, An EQ can cut frequencies too. The right kind of EQ could probably do close to the same thing couldn't it? Advantage would be that I could control it from my floorboard.

 

[crane]

On the triaxis group on Yahoo there's a deep mod controlled by.. the triaxis ! it works the same as the 2:90. Schematics and pic availlable on the group.

 

[francm]

Uhmm, An EQ can cut frequencies too. The right kind of EQ could probably do close to the same thing couldn't it? Advantage would be that I could control it from my floorboard.

Yes, you could do that. You could also make the deep mod foot-switchable, per channel, with a stereo footswitch or both channels at once with a dpdt toggle switch & stereo cable.

 

[vitor gracie]

Ok. Is it necessary to COMPLETELY remove the capacitors (yellow sausage things) from the board by clipping them out with a pair of snips? or is any soldering necessary? It would seem to me that if you just clip one end and leave the capacitor on the actual board that it would remove it from the signal chain with out physically taking it off the board? I am asking because I would rather attempt it myself then pay someone $75-$250 (Trace from Voodoo Amps quoted a rough estimate of $275 to do that and some other things)

Any thoughts?

 

[crane]

The best way is to unsolder one of the cap's lug and let the other. So if you don't like the mod you can easily undone it.

 

[Dewdman42]

Vitor, please let us know how you like it after you do it.

 

[vitor gracie]

Ok, just finished the "Deep Mod" It is WAY WAY easier then I thought it would be. If you have ever soldered a new pick-up in your guitar then you can do this mod.

I printed all the photos of the board and took them into the garage and did it in like 30 minutes. The board is held in place by plastic tabs that need to be squeezed together with a pair of small tweezers to release them from the PC board. There are several of them and it takes time to make sure you are not bending any other capacitors, etc, on the board. Once you have removed the board from its tabs lift it up a bit above the metal frame of the 20/20 to allow access to the capacitors you'll be removing. With a soldering iron, heat the back of the trace just as everyone has said until it loosens the capacitor on the front of the board and pull it off the board when it melts the solder enough to do so. I was overly carefull and realized there is not much to screw up.

The sound is noticabley "bigger" I actually got way better results running it in stereo after the mod for some reason. Let me also just say this; to my ears the Triaxis is a BAD MATCH with a stock 20/20 power amp. The 20/20's configuration really works against the Triaxis' voicing and bottom end. EL-84s don't really do the preamp justice at all, and this was confirmed to me in a long conversation with Trace from Voodoo Amps. He recommended building a custom MM Transformer among other things to do what I am looking for. Again, let me stress that he advised this based on my needs.

I am sure there are others who think it sounds fabulous. I, however, was eventually so frustrated having owned the rig for several weeks now with the sound I was close to selling it. I am much happier with the sound now as it is way more balanced sounding instead of (w/out the mod) missing lows and really pushing some strong frequencies that are at or around 200HZ. (yes, I can hear 200HZ) The amp (when left stock) aggressively cuts lows that you "feel" and need with this preamp. I would say its maybe starting at like 120HZ and drops off from there. All the lows in the Lead Read mode (Orange Recto Channel on mine) are totally gone when its stock to me.

Before doing the mod I plugged the Triaxis into a Class A 30 watt amp's power section to see what the difference was between that and the 20/20. I can't stress enough how colored the 20/20 is EQ-wise. Its really bad to my ears. The 30 watt amp blew it away and made me want to keep the rig and look for options.

So, end result of the Deep Mod to me is it is totally necessary when running a Triaxis. (or any other tube pre) Next step for me is to re-tube the whole rig. This will really make it shine I'm sure. I also am getting a custom ordered Orange 2X12 cab for this rig. (ordered it in black) I think V-30s will be a better match for the tones I want rather then the Black Shadows in my current Mesa 4X12.

My opinion, DO THE MOD!

I'll post some sound clips whenever I can of the rig. Hope that helped, and again, it's all just my opinion.